Web Release Date: March 28,
Synthesis of Contiguous Silica-Gold Core-Shell Structures: Critical Parameters and Processes
and
School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Division of Bioengineering, National University of Singapore, Singapore 117576, and Division of Medical Sciences, National Cancer Centre, Singapore 169610
Received November 16, 2007
Abstract:
A direct process for preparing contiguous gold shells (15-25 nm thick) over amorphous silica spheres (200 nm)
is described. In this method, gold seeds are synthesized from HAuCl4 in a dilute NaOH solution using deposition-precipitation with subsequent metallization by sodium borohydride (NaBH4). The ease of dispersing gold nanocrystals
on spheres of bare silica and spheres after grafting with ammonia was studied as a function of pH (4-8), reaction
temperature (65-96 
C), and time (5-30 min). Additional parameters requiring optimization included the quantity
of NaBH4 and the HAuCl4 in K2CO3 solution to silica volume ratio. The evolution of gold nanocrystal growth was
monitored by transmission electron microscopy, and the bathochromic shift of ultraviolet-visible absorption was
correlated with shell perfection and thickness.
Download the full text: PDF | HTML
